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Patented Dec. 31, 1929 UNITED STATES PATENT OFFICE ALBERT L. CLAPP, O13 DANVEBS, 'MASSACHUSETTS OIL AND GREASE rnoor LINER PAPER R 30am) Am) rnoonss or Max ne sum,

1V0 Drawing.

. This invention is concerned with liner paper or board, possessinghigh oiland greaseproof properties. Such paper is especially adapted formanufacture 'into boxes, cartons 5 andj 'containers, particularly for oily and greasy materials.

The liner paper of the present invention consists of an outer paper ply or liner, which is firmly united with an inner paper ply saturated with setting or. hardening compounds which render it oiland greaseproof.

The inner ply may be produced ,as described in my application for patent, Serial No. 9%,329, filed March 12, 1926, by forming apaper from asbestos and cellulosic fibers, preferably havin lime or equivalent ma terial incorporated therein and then treating the paper with a sodium silicate solution.

The solution reacts with the asbestos to produce throughout the paper a plastic compound which sets or hardens to a ri id con dition and which imparts greasep roo waterproof and fire-resisting properties to the paper. While setting, the sheet acquires a temper o1 consistency permitting it to be bent and stamped into various articles without being cracked or broken, behaving in this respect somewhat like ductile sheet metal, such as sheet tin, zinc, or the like. p In making the paper of the present invention, both plies are preferably formed simultaneously on a multi-cylinder paper machine into faclally contiguous wet webs or layer. The composite paper is then dried, whereupon the inner ply is treated'with suflicientsodium silicate solution, as by a coating operation, to pe'netratetothe outer ply,.so that after drying, the paperwebs are firmly bonded or welded together by the setting compound. The paper is then partially dried,-and upon acquiring the proper temper may be formed into the desired article,

The applicability ofthe present invention maybest be understood by reference to a specific example of procedure such as the following. About 60 parts of cellulose fiber, e. g., sulphite or kraft, and 40 parts of asbestos fiber are placed in the beater engine, and suflicient water is added to ensure circula- 53 tion of the mass. The mass is then thor-- Application filed July 16, 1926, Serial No. 123,021. Renewed June 3, 1929.

oughly intermixed by heating for about twenty minutes, during which time about IQ\% to 15% lime, based on the dry weight offiber,

is preferably added to the" engine and imiformly incorporated into the mass. The furnish is run into one of the vats of a multicylinder paper machine, and a usual papermaking stock, which may, for example, be ordinary bleached sulphite or equivalent fiber, sized as usual, is run into a separate vat. A composite, wet web consisting of an'asbestos-cellulose web and a usual paper web is thus formed. The two webs interlock or mat intimately togetherwhile wet, and upon being dried yield a unitary, composite paper.

The inner or asbestos-cellulose ply is now treated with a sodium silicate solution by passage through any suitable coating or applying machine. A solution prepare by dissolving parts sodiuin silicate Baum) in 50 parts of water i atisfactory for treat- 'ment. Suflicient solution is used to saturate the ply thoroughly to the outer ply. The sodium silicate destroys the fibrous characteristics of the asbestos'and produces a plastic, which behaves somewhat like Portland cement as it becomes set. Immediately after treatment, however, theinner ply is more or less weak and flabby 'and does not permit of successful manipulation, but upon partial drying it acquires the proper temper for bending or folding into cartons, boxes, and the like, without cracking or disintegration. This condition of temper lasts for an hour or so, depending on conditions, so'that the paper may be made into cartons and. boxes by the usual .commercial machines. Such boxes or cartons. are adapted for use with oily and greasy foods, oils, paints and the like. The inner ply is impenetrable by the oil or grease, and thus serves'to. protect the outer ply from becoming stained.

Paper such as herein made has the'agpean ance of ordinary liner paper or paper oard. The liner paperor outside layer may be white or colored, and serves to cover the inner paper or ply, so .that well-appearing cartons or boxes may be made. The liner paper may" also serve as a base or back round for printing. The inner or protecting ply, in midi- 100 tion to its greaseproof and waterproof properties, serves as a rigidifying or stiffenmg material, so that by forming the inner ply as a paper of 7 to 8 points, and the, outer ply of about the same thickness, a paper is pro- .duced which is in effect about as still and rigid as an ordinary 40 point paper-board.

In certain instances, therefore, it may be desirable to use a greaseproof paper such as herein produced as anintermediate or as an outer ply in a multi-ply paper, to stiffen the same and to impart other desirable properties thereto.

The procedure hereinbefore set forth is, of course, subject to variation. Thus, the inner and outer plies need not be united while wet, but may be formed as separate webs and dried. The outer layer may'then be saturated with sodium silicate solution to produce the gummdyl lsetting compound which may serve as an a esive for uniting the two-plies, or any other desired adhesive may be used.

It is obvious that the components of the furnish for the inner ply may be varied in proportion. In the example given, other proportions of asbestos and. cellulose fiber may be used, but in general, approximately equal vparts of the two fibers should be em ployed. The proportion of lime in the furnish may be varied'and, in fact, dispensed with, although foroptimum results lime or equivalent material, such as Portland cement and magnesium oxide, should be employed.

If the percentage of lime is raised to a sufii- 5 cient-1y high figure, say 20%, the use of asbestos fiber may also be dispensed with, but,

inasmuch as this leads to interior results, asbestos fiber is preferably employed.

Having thus described the nature of this 40 invention and a way of making and using the same, although withoutattempting to set forth all the forms in which it may be made or all the modes of its use,

What I claim is:

1. A process which comprises forming paper webs, one of said webs being filled with material capable of reacting with sodium silicate to produce a hardening compound, unit- 1n the webs while wet, and treating the filled 6o wb with sutlicient sodium silicate to penetrate to the other web, thereby firmly bonding together the webs with the hardening compound.

2. A process which comprises forminga 65 liner paper and a paper filled with material capable of reacting with sodium silicate to produce a hardening compound, uniting the paper webs while wet, drying the composite web, and treating the filled web with sulficient sodium silicate to penetrate to the other web, thereby firmly bonding together the webs with the hardening compound.

3. A process which comprises forming a liner paper and a paper filled with material 6 capable of reacting with sodium silicate to produce a hardening compound, uniting the webs while wet, drying the composite web, treating the filled web with sutlicient sodium silicate to penetrate to the other web, thereby firmly bonding together the webs with the hardening compound, forming the treated paper into an article of the desired shape, and allowing the article to set or harden.

l. A process which comprises forming a liner paper and a paper comprising'cellulosc and asbestos fiber, uniting the paper webs, and treating the asbestos-cellulose web with sutficient sodium silicate to penetrate to the other web, thereby firmly bonding together the webs with the hardening compound.

5. A. process which comprises forming a liner paper and a cellulose-asbestosfiber paper filled with lime, uniting the paper webs while wet, drying the composite web, and treating the asbestos-cellulose web with sutlicient sodium silicate to penetrate to the other web, thereby firmly bonding together the webs with the hardening compound.

6. A process which comprises forming a composite web comprising a liner paper and a cellulose-asbestos paper, treating the celhn lose-asbestos paper-with sullicient sodium s:ili-' cute to penetrate to the other web, thereby firmly bonding together the webs with the hardening compound, forming the treatedcomposite web into an article of the desired shape, and allowing the article to set.

8. A composite, greasep'roof paper consisting of a paper ply permeated with a hardening compound and united and firmly honded together by said compound with another paper ply.

8. A composite. greaseproof paper consisting of a paper ply permeated with the setor hardened compound of asbestos and sodium silicate and intimately united and firmly bonded together by said compound with another paper ply.

- 9. A composite, greascproof paper consisting of a paper ply permeated with the set no or hardened compound of asbestos, lime and sodium silicate, intimately united and firmly bonded together by said compound with another paper ply.

10. A multi-ply, grcascproof paper, certain only of the plies being urn eated with a set or hardened compound of asbestos and sodium silicate, said compound firmly bonding together the plies of said paper.

In testimony whereof I. have allixed my signature.

ALBERT L. CLAPP. 

